If the temperature of a tank storing a high-pressure gas increases by fire or the like, the tank may burst. Therefore, the tank is provided with a pressure relief valve. When the temperature around the tank becomes a predetermined temperature, the pressure relief valve releases the gas to the atmosphere. Known as the pressure relief valve is, for example, a pressure relief valve device disclosed in PTL 1.
According to the pressure relief valve device of PTL 1, a fusible piece supports a valve element, and the position of the valve element is maintained at a closed position at which the valve element closes a valve passage. The fusible piece melts at a predetermined melting temperature to be discharged to the atmosphere. The valve element is biased by a spring member toward an open position. When the fusible piece is discharged, the valve element moves to the open position. With this, the valve passage opens, and the gas is released to the atmosphere.